A Cochrane review included 6 studies with a total of 1 162 subjects. Three studies compared 2 g of preoperative amoxicillin versus placebo, one compared 3 g of preoperative amoxicillin versus placebo, one compared 1 g of preoperative amoxicillin plus 500 mg 4 times a day for 2 days versus no antibiotics, and one compared four groups: (1) 2 g of preoperative amoxicillin; (2) 2 g of preoperative amoxicillin plus 1 g twice a day for seven days; (3) 1 g of postoperative amoxicillin twice a day for 7 days, and (4) no antibiotics. The meta-analyses showed a statistically significant higher number of patients experiencing implant failures in the group not receiving antibiotics (table ). The number needed to treat (NNT) to prevent one patient having an implant failure is 25 (95% CI 14 to 100), based on a patient implant failure rate of 6% in patients not receiving antibiotics.
| Outcome | Relative effect (95% CI) | Assumed risk – without antibiotic* | Corresponding risk –antibiotic (95% CI) | Participants (studies) |
|---|---|---|---|---|
| *placebo in 4 studies and no antibiotic in 2 studies | ||||
| Implant failure at 4 months | RR 0.33 (0.16 to 0.67) | 10 per 1000 | 4 per 1000 (2 to 7) | 1 162 (6) |
There was borderline statistical significance for prosthesis failures (RR 0.44, 95% CI 0.19 to 1.00), with no statistically significant differences for infections (RR 0.69, 95% CI 0.36 to 1.35), or adverse events (RR 1, 95% CI 0.06 to 15.85; only two minor adverse events were recorded, one in the placebo group). No conclusive information can be derived from the only study that compared three different durations of antibiotic prophylaxis since no event (implant/prosthesis failures, infections or adverse events) occurred in any of the 25 participants included in each study group. There were no studies evaluating different antibiotics or different antibiotic dosages.